Method for rapidly operating ground equipment embodying hydraulic system using all season petroleum hydraulic fluid

ABSTRACT

A SINGLE HYDRAULIC FLUID PETROLEUM BASE BLEND CONSISTING OF A HIGHLY REFINED PETROLEUM FRACTION OF A NAPHTHENIC COASTAL CRUDE, SAID CRUDE BEING HYDROGENATED, SOLVENT REFINED AND FRACTIONATED, SAID BLEND HAVING A VISCOSITY 1.32 CETISTOKES AT 98.9* C. AND 381 CENTISTOKES AT -53.9* C. AND POSSESSING GOOD OXIDATION STABILITY, GOOD RUST PROTECTION AND GOOD ANTIWEAR PROPERTIES ACHIEVED BY ADDITION OF TRICRESYL PHOSPHATE, PHENYL-1-NAPHTHYLAMINE AND BARIUM DINONYLNAPHTHYLENE SULFONATE, IS APPLIED TO THE HYDRAULIC SYSTEM OF GROUND EQUIPMENT, AND THE TURRET SYSTEM OF SAID GROUND EQUIPMENT IS OPERATED CONTINUOUSLY FOR AT LEAST 213 HOURS.

United States Patent METHOD FOR RAPIDLY OPERATING GROUND EQUIPMENT EMBODYING HYDRAULIC SYS- TEM USING ALL SEASON PETROLEUM HY- DRAULIC FLUID Joseph F. Messina, Havertown, and Abraham Mertwoy, Dresher, Pa., assignors to the United States of America as represented by the Secretary of the Army No Drawing. Continuation-impart of abandoned application Ser. No. 74,142, Sept. 21, 1970. This application Nov. 11, 1971, Ser. No, 197,944

Int. Cl. C09k 3/02 US. Cl. 252-75 2 Claims ABSTRACT OF THE DISCLOSURE A single hydraulic fluid petroleum base blend consisting of a highly refined petroleum fraction of a naphthenic coastal crude, said crude being hydrogenated, solvent refined and fractionated, said blend having a viscosity 1.32 centistokes at 98.9 C. and 381 centistokes at 53.9 C. and possessing good oxidation stability, good rust protection and good antiwear properties achieved by addition of tricresyl phosphate, phenyl-1-naphthylamine and barium dinonylnaphthylene sulfonate, is applied to the hydraulic system of ground equipment, and the turret system of said ground equipment is operated continuously for at least 213 hours.

This application is a continuation-in-part of patent application, Ser. No. 74,142 of Joseph F. Messina and Abraham Mertwoy for All Season Petroleum Hydraulic Fluid, filed Sept. 21, 1970, and now abandoned, assigned to the same assignee hereof.

The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to use of any royalty thereon.

This invention relates to'hydraulic fluids and more particularly concerns a very low viscosity petroleum base hydraulic fluid which permits rapid operation of group equipment at extremely low temperatures and unexpectedly good performance at bulk fluid temperatures of 98.9 C.

Hydraulic fluid, petroleum base, preservative, meeting Specification MIL-H-6083B, July 1957, is currently used for ground equipment by the US. Army as an operational and preservative fluid (MILH6083C, Amendment 2, June 1969, in certain aspects neither of which specifications are significant for the purposes of this invention). In recent performance tests on M48A2 and M60 tanks, both of which use the same hydraulic gun control system, it was found that their g-un elevating and turret traversing systems would not function at 53.9 C. when using MIL- H-6083B hydraulic fluid. Since movement of the turret and gun are dependent on the amount of fluid under pressure delivered to the traversing gear box hydraulic motor assembly and to the elevating mechanism respectively, it becomes apparent that a principal cause of their inorperability is due to the fact that their hydraulic systems, as designed, cannot move efficiently, since fluids used therein have viscometric values of about 4500 centistokes, i.e., the viscosity of MIL-H-6083B fluid at -53.9 C.

Because it is neither economically feasible to modify the large number of tanks involved, in order to achieve alltemperature operation with a single fluid, nor logistically sound to depend on two fluids to cover low and high temperature operation, notwithstanding the attendant storage and handling problems, the development of a single hydraulic fluid to permit operation of existing equipment over the wide service temperature range becomes extremely important. Not only must this hydraulic fluid have suitable viscometric properties to permit optimum performance at all temperatures, i.e., at both -53.9 C. and 98.9 C., but it also must provide good rust protection, effective antiwear and oxidation stability, and exhibit minimum foaming and leakage characteristics. In addition, the fluid must be from a petroleum base stock to permit compatibility with seals, packings and O-rings formed in existing military ground equipment.

It is therefore an object of this invention to provide a single hydraulic fluid which may be advantageously used at temperature extremes.

Another object of the invention is to provide such a fluid having good rust protection, antiwear and oxidation stability.

A further object of the invention is to provide such a fluid which will permit continuous cycling of a tank gun and turret for operational periods far in excess of expected combat conditions.

These and further objects and advantages of the invention will be apparent as the description of the invention proceeds.

In accordance with the aforementioned objects, we have discovered and developed a single hydraulic fluid which permits effective and extended operation of ground equipment, and especially the US. Armys M48A2 and M battle tanks over the temperature range from 53.9 C. to 98.9 C. Immediate economics realized through the use of this fluid are the elimination of the need for:

(1) Several fluids of different viscosities to cover the desired operating temperature range.

(2) Hardware modification and retrofit of existing tanks.

(3) Installation of auxiliary heating equipment.

The latter two would be necessary in order to permit the use of presently specified MIL-6083B hydraulic fluids at -53.9 C. It must be continuously borne in mind that the inventive hydraulic fluid must perform satisfactorily not only at -53.9 C., but when tested at elevated temperatures up to 98.9 C., the fluid must yet retain its protective properties.

Preliminary performance tests on a presently qualified petroleum fluid meeting MIL-H6083B requirements, having 4500 centistokes at S3.9 C. and 10 centistokes at 54.4 C., permitted a maximum rotational speed for gun and turret of 215 mils per second at -31.6 C. after about 5 seconds of operation. 200 mils per second within 18 seconds was considered acceptable for operation at S3.9 C.

Since the viscosity of the MIL-H-6083B hydraulic fluid at 31.6 C. was found to be 350 centistokes, this value might be the viscosity needed for satisfactory operation of the gun control system at 53.9 C. A relatively low aromatic, petroleum base stock having such viscometric properties was thus obtained. Physical and chemical characteristics of the high aniline point base fluid selected are given in Table I below along with our final blend.

TABLE I.PROPERTIES OF BASE FLUID AND FINAL BLEND Test method Base fluid Final blend Viscosity, centistokes:

98.9 C 1.0- ASTM D 445 70.0 7 -53.9 C 250.0 381.00 Flash point, C ASTM D 92 93.3 Fire point, C ASTM D 92 ASTM D 7 59 Below -567 Pour point, C Low temperature stability at 53.9 C., 72 hours.-.

Acid No Carbon residue. Aniline point. Insol., g./l00 ml Rubber swell, percent L-stock at 70 C. for 168 hours. Clay-gel analysis, wt., percent:

A snh alfencs 9 Fed. Std. Test Method 3459--..

Fed. Std. Test Method 5106.... AMSTM D 524 ASTM D 611 Fed. Std. Test Method 5308..-.

saturates Galvanic corr inn Fed. Std. Test Method 5322-1" Pass Pass. Anti-Wear, scar dia., mm.:

s }Fed. Std. Test Method 6514 0. 40 kg. 0.846---- 0.758. am:

23.9 C Complete collapse within S D 392 30 seconds. 933 C Complete collapse within 10 seconds. Rust protection Cyclic humidity cabinet 24 hours 216 hours.

' Four-Ball tester +75 0., 1,200 r.p.m. for one hour.

b Determined in the Frankford Arsenal cyclic humidity cabinet, in which 1,020 steel cylindrical rods x 4" were coated with the test oils and exposed to alternating cycles of 4 hours at 43.3" C. and 80% RH followed by 4 hours at 54.4 C. and 95% RH.

The base fluid may be a low viscosity petroleum fraction of a naphthenic coastal crude. The crude i hydrogenated, solvent refined and fractionated. The cut used has a boiling point range from 420 F. to 550- F. as indicated below:

The cut has a flash point of 200 F., a fire point of 220 F. and a pour point of -70 F. The carbon residue is 0.05 and a minimum aniline point of 150. The clay-gel analysis (wt., percent) is as follows:

Asphaltenes 0.5 Polar 2.0 Aromatics 25.0 Saturates 70.0

Comparative performance tests were then conducted with the petroleum base tock and a MIL-H-6083B fluid in an M48A2 tank. It was found that from C. to 52 C., the performance of the two fluids was nearly the same. As the temperature dropped, however, differences in performance became very pronounced as shown by the fact that at -40 C., the MIL-H-6083B hydraulic fluid permitted a rotational speed of 140 mils per second and the low viscosity fluid 350 mils per second. These speeds were achieved five seconds after the gunner set his control for maximum slew rate. At 53.9 C., the base fluid permitted speeds of 200 mils per second after 15 seconds and 426.7 mil per second after four minutes of operation. In contrast, MIL-H-6083B fluid, after a starting rotational speed of approximately 15 mils per second at -53.9 C. permitted the turret to rotate only 300 mils per second after minutes of operation. The original premise that satisfactory operation of the turret at -53.9 0., could be achieved with a fluid having a viscosity of approximately 350 ccntistokes was borne out by the fact that the base fluid permitted rotational speeds of 200 mils TABLE II.COMPOSITION OF FINAL BLEND Composition: Wt., percent Base oil 95.0 Tricresyl phosphate 1.5 Phenyl-l-naphthylamine 0.5 Barium dinonylnaphthylene sulfonate 3.0

Tricresyl phosphate is a known antiwear agent and may be present in quantities ranging'between about 0.5 to 3.0 weight percent. Similarly, phcnyll-naphthylamine and barium dinonylnaphthylene sulfonate are known oxidation and rust inhibitors respectively. Effective ranges of these two compounds are about 0.1 to 1.0 and 1.0 to 10.0 weight percent respectively.

Since the base fluid used in formulating our final blend represented a very low viscosity petroleum fraction (1.00 centistoke at 98.9" C., 250 ccntistokes at 53.9 C.), it was mandatory that performance tests be conducted on M48A2 tanks to determine whether such an extremely low viscosity fluid would perform satisfactorily over long periods of time at elevated temperatures, particularly with respect to response rates, leakage and wear. Accordingly, the turret and gun hydraulic control system of an M48A2 tank was completely disassembled and its parts examined for compliance with specifications. Micrometer measurements were made on the pistons and cylinders in the traversing motor. The latter was selected for very close examination because it is the prime component controlling turret performance. This is based on the fact that turret velocity is dependent upon the speed attained by the traversing motor when fluid is directed through it, in a manner very similar in principle to a water Wheel. It is obvious, therefore, that as the driving fluid increases in viscosity, as the ambient temperature decreases, operation of the traversing motor will become sluggish and the turret velocity will decrease. Conversely, as the ambient temperature goes up and the viscosity of the hydraulic fluid decreases, turret velocity will improve to an optimum. Peak performance can be expected thereafter for an indefinite range of temperature increases. Ultimately, however, temperatures and viscosities reach a point where leakage, loss of precision control and the possibility of excessive wear of moving parts may be expected.

The hydraulic system was then reassembled using new buna-N O-rings, gaskets and seals and the turret was placed on a supporting stand. Due to space limitations of the environmental test chamber, the gun tube was removed and weights substituted so that the center of gravity of the turret remained the same. These modifications in no way altered the performance characteristics of the gun and turret which is independent of the vehicle body. The test unit was allowed to soak overnight at an ambient temperature of 51.7 C. in a climatic chamber. The gunners control was then set to rotate the turret at 50 mils per second which quickly brought the bulk fluid temperature up to an average of 98.9 C. No leaks were observed in the hydraulic system over the life of the test which was terminated after 213 hours.

At this time, the hydraulic system was disassembled and measurements made on the pistons and cylinders of the traversing motor. The diametrical clearances, i.e., the difference between piston diameter and cylinder diameter, at the start of the test averaged 0.0012 inch; after 213 hours, clearances averaged 0.0014 inch. A diametrical clearance of 0.003 inch would still permit satisfactory operation of the gun and turret. The components, therefore, were not only in excellent condition but in fact could have been used once again for additional performance tests.

It must be herein emphasized that notwithstanding our blend consists of a highly refined petroleum fraction (which is somewhat similar to kerosene and compatible with seals, packings and O-rings used in existing military ground equipment) which may be prepared commercially and made available by special order, and additives which impart their expected function, the ability of this blend to operate not only at temperatures as low as 53.9 C., but at least equally important, the ability of this extremely low viscosity blend to operate most satisfactorily at both this low temperature and at temperatures as high as 98.9 C. without excessive wear of parts was unexpected and highly unpredictable. Even more startling however, was the discovery that this extremely low viscosity fluid actually provided at least 213 hours of continuous cycling of gun and turret, which, as aforementioned, represents, operational time far beyond that normally specified for overhaul. Additionally, the long sought-for solution by the U.S. Army for such a single fluid blend capable of satisfactorily performing over the aforementioned temperature range has finally been achieved after over a decade of intensive investigation.

We wish to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

We claim:

1. A method for rapidly operating ground equipment over the temperature range of 53.9 C. to 98.9 C. by a single hydraulic fluid petroleum base blend, said blend consisting of a highly refined petroleum fraction of a naphthenic coastal crude, said crude being hydrogenated, solvent refined and fractionated, said blend having a viscosity of 1.32 centistokes at 98.9 C. and 381 centistokes at -53.9 C., said blend possessing good oxidation stability, good rust protection and good antiwear properties, said oxidation stability, rust protection and antiwear properties being achieved by the addition of 0.5 to 3.0 weight percent tricresyl phosphate, 0.1 to 1.0 weight percent phenyl-l-naphthylamine, and 1.0 to 10.0 weight percent barium dinonylnaphthylene sulfonate, and comprising the steps of applying said blend to the hydraulic system of ground equipment, and operating continuously the turret system of said hydraulic system for a period of at least 213 hours, said period being far in excess of that normally specified for said hydraulic system, and said petroleum base having physical properties as set forth in column headed Base Fluid in Table I of specification.

2. The method as described in claim 1, said blend consisting of 1.5 weight percent tricresyl phosphate, 0.5 weight percent phenyl-l-naphthylamine, 3.0 weight percent barium dinonylnaphthylene sulfonate, and 95 weight percent of said petroleum base.

References Cited UNITED STATES PATENTS 2,528,348 10/ 1950 Denison et al. 252 2,614,390 10/1952 Poitras et al 89 41 H X 2,616,854 11/1952 Fenske 25273 X 3,080,330 3/1963 Rudel et al 252- 59 X 3,156,652 11/1964 Foehr 25275 3,598,738 8/1971 Biswell et al. 25273 X RICHARD D. LOVERING, Primary Examiner U.S. Cl. X.R. 

